1. Field of the Invention
This invention generally relates to music apparatus. In particular, the invention is directed to efficient access to a desired chord progression, evaluating suitability between a chord progression and a melody, harmonizing a melody based on the suitability evaluating, and editing a chord progression of a music piece.
2. Description of the Prior Art
Chord progression apparatus which produce a musical chord progression are known in the art of electronic musical instruments or systems. The prior art chord progression apparatus are classified into two distinct categories. In the first category, chord progression apparatus makes a chord progression without any melody (i.e., before any melody is supplied). Thus, the chord progression apparatus in this group are primarily for those users who wish to compose a melody based on a chord or harmony progression (made by the apparatus). The first classified chord progression apparatus should be called "harmony first chord progression apparatus." Chord progression apparatus in the second category make a chord progression after a melody is given. The focus of the apparatus is to make a chord progression suitable for the given melody. Thus, the chord progression apparatus in the second group are helpful for those who have no or little knowledge of harmony. The best name of these apparatus may be "melody first chord progression apparatus" or "melody harmonizing apparatus."
A prior art chord progression apparatus of the harmony first type (disclosed in Japanese patent application laid open to public as Hei 1-262595, Oct. 19, 1989) applies Markov process to transitions from one chord to another. The chord transition table memory describes what chords are more likely or less likely to come after a chord. Probability values from the transition table are combined with random numbers generated by an electronic pseud random number generator to determine a succeeding chord. Repeating the process, the apparatus makes a chord progression (succession of chords) of any desired length. Because of the principles, the apparatus cannot hope to provide various kinds of chord progressions. Users of the apparatus cannot hope to get a desired chord progression in an efficient way.
Another prior art chord progression apparatus of the harmony first type is disclosed in U.S. patent application Ser. No. 07/411,541, filed Sep. 22, 1989 and assigned to the same assignee as the present application. The apparatus applies a theory of functional harmony to the making of a chord progression. According to the functional harmony theory, a chord progression can be analyzed as a chain of short function patterns, each element of which is one of the three functions: tonic (T), dominant (D) and subdominant (S). The apparatus has a function pattern file memory which stores a set of short function patterns, and a chord pattern file memory which stores a set of (root and type specified) chord patterns arranged in groups according to function patterns. In operation, to make (synthesize) a chord progression, the apparatus forms a chain of short function patterns and then converts each function pattern in the chain to a root and type specified chord pattern. Therefore, the apparatus is useful as an educational tool for learning the functional harmony theory. However, it has limited capability of producing practical chord progressions: practical chord progressions often include those chords having no harmonic function, as analysts of practical music point out. Therefore, users of the apparatus will find it difficult to get a desired chord progression which should be practical and real.
Prior art chord progression apparatus of the melody first type i.e., melody harmonizing apparatus are disclosed in Japanese patent application laid open to public as Sho 58-87593, May 25, 1983, and U.S. Pat. No. 4,539,882, Sep. 10, 1985.
Each apparatus relies on several inaccurate or unnecessary assumptions. Among them are (a) no change of key throughout a given melody, (b) diatonic scale notes (on a single key) occupy predominant proportion of a given melody, (c) particular tonal function of last melody notes, (d) no change of harmony (chord) within a bar (i.e., harmony can change only at a bar-line), and (e) harmonic tones (chord tones) always occupy predominant proportion of a melody even if it is a small melody segment as short as one bar. Based on the assumptions (a) to (c), each apparatus determines a single key of a given melody. According to the assumption (d), each apparatus subdivides a given melody into a plurality of small blocks (one-bar melody segments). Then, each apparatus successively determines chords for the melody segments, one chord after another in a forward direction from start to end of the given melody. To determine a chord for a succeeding bar melody segment, the apparatus of the Japanese patent application Sho 58-87593 matches the pitch collection of each chord candidate to that of the melody segment to compute a pitch similarity index for each chord candidate; this matching is based on the assumption (e). The apparatus looks up a statistical table which describes statistics of transitions between two chords. The pitch similarity indexes are combined with the statistical likelihood of chord transitions to determine a single chord for the succeeding melody segment. For the same purpose, the apparatus of U.S. Pat. No. 4,539,882 focuses on main note(s) in a succeeding bar melody segment: the main notes are defined by longest notes, which are presumed harmonic tones (see assumption (e) above). Then apparatus looks up a statistical table which describes transitions to main note(s) from a preceding chord, and returns a succeeding chord (which is used as the chord for the succeeding melody segment).
Each of the two apparatus has the following drawbacks: (A) it cannot control unit/variety balance of a chord progression for a given melody because each apparatus determines chords separately and singly for each melody segment, (B) harmonic rhythm is always made simple and primitive because of the assumption (d) above, (C) each apparatus cannot provide satisfactory harmonization of a melody without modulation, (D) chord progression is made up of diatonic chords only, and (E) each apparatus is inapplicable to the making of a chord progression without a melody.
Another prior art melody harmonization apparatus is disclosed in U.S. Pat. No. 4,951,544, issued on Aug. 28, 1990 to J. Minamitaka (present inventor) and assigned to the same assignee as the present application. The apparatus determines available chords as many as there are for each segment (e.g., bar) of a given melody. To this end, the apparatus scans a set of chord candidates. Each chord candidate is tentatively assumed available for a melody segment of interest. Then melody tones in the melody segment are analyzed and identified in a forward reasoning by exploring a network of stored musical knowledge of classifying melody tone functions while checking local melodic waves. The reasoning continues either until a counterexample of the tentative assumption is found or until verification of the assumption has been made as the case may be. The associated chord candidate is determined available in the latter case and unavailable in the former case. By repeating the available chord determining process for each segment of a given melody, the apparatus forms a two dimensional array of available chord progressions for the entire melody. Then, the apparatus selects chords from the array, one for each melody segment in accordance with tonality-based selection criteria.
While the apparatus overcomes or ameliorates some disadvantages of the two prior harmonizing apparatus mentioned earlier, it still has problems to be solved: (P1) the apparatus is designed for the melody harmonizing application only, (P2) selection of chords is made one by one, thus limiting real harmonization capabilities, and (P3) harmonic rhythm is made simple, or less active.
In summary, no prior art chord progression apparatus provide a convenient environment in which users can easily get the desired chord progression. None of the prior art chord progression apparatus is applicable to both tasks of melody harmonization and making of a chord progression without a melody. No prior art apparatus are so helpful as the invention for those users having insufficient musical knowledge or experience to compose a music piece. No prior art chord progression apparatus have capability of editing a chord progression of a music piece to aid user's music compostion. No prior art melody harmonization apparatus take a chord progression (rather than a chord) as an integrated and coherent entity or unit for harmonizing a melody, apply a chord progression for one time to a relatively long melody segment (i.e., phrase), or test suitability of a chord progression candidate for a phrase melody based on stored musical knowledge of melodies.
These problems are successfully overcome by the invention, as will be understood from the following description.